minix/kernel/mpx386.s

# 
! This file, mpx386.s, is included by mpx.s when Minix is compiled for 
! 32-bit Intel CPUs. The alternative mpx88.s is compiled for 16-bit CPUs.

! This file is part of the lowest layer of the MINIX kernel.  (The other part
! is "proc.c".)  The lowest layer does process switching and message handling.
! Furthermore it contains the assembler startup code for Minix and the 32-bit
! interrupt handlers.  It cooperates with the code in "start.c" to set up a 
! good environment for main().

! Every transition to the kernel goes through this file.  Transitions to the 
! kernel may be nested.  The initial entry may be with a system call (i.e., 
! send or receive a message), an exception or a hardware interrupt;  kernel 
! reentries may only be made by hardware interrupts.  The count of reentries 
! is kept in "k_reenter". It is important for deciding whether to switch to 
! the kernel stack and for protecting the message passing code in "proc.c".

! For the message passing trap, most of the machine state is saved in the
! proc table.  (Some of the registers need not be saved.)  Then the stack is
! switched to "k_stack", and interrupts are reenabled.  Finally, the system
! call handler (in C) is called.  When it returns, interrupts are disabled
! again and the code falls into the restart routine, to finish off held-up
! interrupts and run the process or task whose pointer is in "proc_ptr".

! Hardware interrupt handlers do the same, except  (1) The entire state must
! be saved.  (2) There are too many handlers to do this inline, so the save
! routine is called.  A few cycles are saved by pushing the address of the
! appropiate restart routine for a return later.  (3) A stack switch is
! avoided when the stack is already switched.  (4) The (master) 8259 interrupt
! controller is reenabled centrally in save().  (5) Each interrupt handler
! masks its interrupt line using the 8259 before enabling (other unmasked)
! interrupts, and unmasks it after servicing the interrupt.  This limits the
! nest level to the number of lines and protects the handler from itself.

! For communication with the boot monitor at startup time some constant
! data are compiled into the beginning of the text segment. This facilitates 
! reading the data at the start of the boot process, since only the first
! sector of the file needs to be read.

! Some data storage is also allocated at the end of this file. This data 
! will be at the start of the data segment of the kernel and will be read
! and modified by the boot monitor before the kernel starts.

! sections

.sect .text
begtext:
.sect .rom
begrom:
.sect .data
begdata:
.sect .bss
begbss:

#include <minix/config.h>
#include <minix/const.h>
#include <minix/com.h>
#include <ibm/interrupt.h>
#include "const.h"
#include "protect.h"
#include "sconst.h"

/* Selected 386 tss offsets. */
#define TSS3_S_SP0	4

! Exported functions
! Note: in assembly language the .define statement applied to a function name 
! is loosely equivalent to a prototype in C code -- it makes it possible to
! link to an entity declared in the assembly code but does not create
! the entity.

.define	_restart
.define	save

.define	_divide_error
.define	_single_step_exception
.define	_nmi
.define	_breakpoint_exception
.define	_overflow
.define	_bounds_check
.define	_inval_opcode
.define	_copr_not_available
.define	_double_fault
.define	_copr_seg_overrun
.define	_inval_tss
.define	_segment_not_present
.define	_stack_exception
.define	_general_protection
.define	_page_fault
.define	_copr_error

.define	_hwint00	! handlers for hardware interrupts
.define	_hwint01
.define	_hwint02
.define	_hwint03
.define	_hwint04
.define	_hwint05
.define	_hwint06
.define	_hwint07
.define	_hwint08
.define	_hwint09
.define	_hwint10
.define	_hwint11
.define	_hwint12
.define	_hwint13
.define	_hwint14
.define	_hwint15

.define	_s_call
.define	_p_s_call
.define	_level0_call

! Exported variables.
.define	begbss
.define	begdata

.sect .text
!*===========================================================================*
!*				MINIX					     *
!*===========================================================================*
MINIX:				! this is the entry point for the MINIX kernel
	jmp	over_flags	! skip over the next few bytes
	.data2	CLICK_SHIFT	! for the monitor: memory granularity
flags:
	.data2	0x01FD		! boot monitor flags:
				!	call in 386 mode, make bss, make stack,
				!	load high, don't patch, will return,
				!	uses generic INT, memory vector,
				!	new boot code return
	nop			! extra byte to sync up disassembler
over_flags:

! Set up a C stack frame on the monitor stack.  (The monitor sets cs and ds
! right.  The ss descriptor still references the monitor data segment.)
	movzx	esp, sp		! monitor stack is a 16 bit stack
	push	ebp
	mov	ebp, esp
	push	esi
	push	edi
	cmp	4(ebp), 0	! monitor return vector is
	jz	noret		! nonzero if return possible
	inc	(_mon_return)
noret:	mov	(_mon_sp), esp	! save stack pointer for later return

! Copy the monitor global descriptor table to the address space of kernel and
! switch over to it.  Prot_init() can then update it with immediate effect.

	sgdt	(_gdt+GDT_SELECTOR)		! get the monitor gdtr
	mov	esi, (_gdt+GDT_SELECTOR+2)	! absolute address of GDT
	mov	ebx, _gdt			! address of kernel GDT
	mov	ecx, 8*8			! copying eight descriptors
copygdt:
 eseg	movb	al, (esi)
	movb	(ebx), al
	inc	esi
	inc	ebx
	loop	copygdt
	mov	eax, (_gdt+DS_SELECTOR+2)	! base of kernel data
	and	eax, 0x00FFFFFF			! only 24 bits
	add	eax, _gdt			! eax = vir2phys(gdt)
	mov	(_gdt+GDT_SELECTOR+2), eax	! set base of GDT
	lgdt	(_gdt+GDT_SELECTOR)		! switch over to kernel GDT

! Locate boot parameters, set up kernel segment registers and stack.
	mov	ebx, 8(ebp)	! boot parameters offset
	mov	edx, 12(ebp)	! boot parameters length
	mov	eax, 16(ebp)	! address of a.out headers
	mov	(_aout), eax
	mov	ax, ds		! kernel data
	mov	es, ax
	mov	fs, ax
	mov	gs, ax
	mov	ss, ax
	mov	esp, k_stktop	! set sp to point to the top of kernel stack

! Call C startup code to set up a proper environment to run main().
	push	edx
	push	ebx
	push	SS_SELECTOR
	push	DS_SELECTOR
	push	CS_SELECTOR
	call	_cstart		! cstart(cs, ds, mds, parmoff, parmlen)
	add	esp, 5*4

! Reload gdtr, idtr and the segment registers to global descriptor table set
! up by prot_init().

	lgdt	(_gdt+GDT_SELECTOR)
	lidt	(_gdt+IDT_SELECTOR)

	jmpf	CS_SELECTOR:csinit
csinit:
    o16	mov	ax, DS_SELECTOR
	mov	ds, ax
	mov	es, ax
	mov	fs, ax
	mov	gs, ax
	mov	ss, ax
    o16	mov	ax, TSS_SELECTOR	! no other TSS is used
	ltr	ax
	push	0			! set flags to known good state
	popf				! esp, clear nested task and int enable

	jmp	_main			! main()


!*===========================================================================*
!*				interrupt handlers			     *
!*		interrupt handlers for 386 32-bit protected mode	     *
!*===========================================================================*

!*===========================================================================*
!*				hwint00 - 07				     *
!*===========================================================================*
! Note this is a macro, it just looks like a subroutine.
#define hwint_master(irq)	\
	call	save			/* save interrupted process state */;\
	push	(_irq_handlers+4*irq)	/* irq_handlers[irq]		  */;\
	call	_intr_handle		/* intr_handle(irq_handlers[irq]) */;\
	pop	ecx							    ;\
	cmp	(_irq_actids+4*irq), 0	/* interrupt still active?	  */;\
	jz	0f							    ;\
	inb	INT_CTLMASK		/* get current mask */		    ;\
	orb	al, [1<<irq]		/* mask irq */			    ;\
	outb	INT_CTLMASK		/* disable the irq		  */;\
0:	movb	al, END_OF_INT						    ;\
	outb	INT_CTL			/* reenable master 8259		  */;\
	ret				/* restart (another) process      */

! Each of these entry points is an expansion of the hwint_master macro
	.align	16
_hwint00:		! Interrupt routine for irq 0 (the clock).
	hwint_master(0)

	.align	16
_hwint01:		! Interrupt routine for irq 1 (keyboard)
	hwint_master(1)

	.align	16
_hwint02:		! Interrupt routine for irq 2 (cascade!)
	hwint_master(2)

	.align	16
_hwint03:		! Interrupt routine for irq 3 (second serial)
	hwint_master(3)

	.align	16
_hwint04:		! Interrupt routine for irq 4 (first serial)
	hwint_master(4)

	.align	16
_hwint05:		! Interrupt routine for irq 5 (XT winchester)
	hwint_master(5)

	.align	16
_hwint06:		! Interrupt routine for irq 6 (floppy)
	hwint_master(6)

	.align	16
_hwint07:		! Interrupt routine for irq 7 (printer)
	hwint_master(7)

!*===========================================================================*
!*				hwint08 - 15				     *
!*===========================================================================*
! Note this is a macro, it just looks like a subroutine.
#define hwint_slave(irq)	\
	call	save			/* save interrupted process state */;\
	push	(_irq_handlers+4*irq)	/* irq_handlers[irq]		  */;\
	call	_intr_handle		/* intr_handle(irq_handlers[irq]) */;\
	pop	ecx							    ;\
	cmp	(_irq_actids+4*irq), 0	/* interrupt still active?	  */;\
	jz	0f							    ;\
	inb	INT2_CTLMASK						    ;\
	orb	al, [1<<[irq-8]]					    ;\
	outb	INT2_CTLMASK		/* disable the irq		  */;\
0:	movb	al, END_OF_INT						    ;\
	outb	INT_CTL			/* reenable master 8259		  */;\
	outb	INT2_CTL		/* reenable slave 8259		  */;\
	ret				/* restart (another) process      */

! Each of these entry points is an expansion of the hwint_slave macro
	.align	16
_hwint08:		! Interrupt routine for irq 8 (realtime clock)
	hwint_slave(8)

	.align	16
_hwint09:		! Interrupt routine for irq 9 (irq 2 redirected)
	hwint_slave(9)

	.align	16
_hwint10:		! Interrupt routine for irq 10
	hwint_slave(10)

	.align	16
_hwint11:		! Interrupt routine for irq 11
	hwint_slave(11)

	.align	16
_hwint12:		! Interrupt routine for irq 12
	hwint_slave(12)

	.align	16
_hwint13:		! Interrupt routine for irq 13 (FPU exception)
	hwint_slave(13)

	.align	16
_hwint14:		! Interrupt routine for irq 14 (AT winchester)
	hwint_slave(14)

	.align	16
_hwint15:		! Interrupt routine for irq 15
	hwint_slave(15)

!*===========================================================================*
!*				save					     *
!*===========================================================================*
! Save for protected mode.
! This is much simpler than for 8086 mode, because the stack already points
! into the process table, or has already been switched to the kernel stack.

	.align	16
save:
	cld			! set direction flag to a known value
	pushad			! save "general" registers
    o16	push	ds		! save ds
    o16	push	es		! save es
    o16	push	fs		! save fs
    o16	push	gs		! save gs
	mov	dx, ss		! ss is kernel data segment
	mov	ds, dx		! load rest of kernel segments
	mov	es, dx		! kernel does not use fs, gs
	mov	eax, esp	! prepare to return
	incb	(_k_reenter)	! from -1 if not reentering
	jnz	set_restart1	! stack is already kernel stack
	mov	esp, k_stktop
	push	_restart	! build return address for int handler
	xor	ebp, ebp	! for stacktrace
	jmp	RETADR-P_STACKBASE(eax)

	.align	4
set_restart1:
	push	restart1
	jmp	RETADR-P_STACKBASE(eax)

!*===========================================================================*
!*				_s_call					     *
!*===========================================================================*
	.align	16
_s_call:
_p_s_call:
	cld			! set direction flag to a known value
	sub	esp, 6*4	! skip RETADR, eax, ecx, edx, ebx, est
	push	ebp		! stack already points into proc table
	push	esi
	push	edi
    o16	push	ds
    o16	push	es
    o16	push	fs
    o16	push	gs
	mov	si, ss		! ss is kernel data segment
	mov	ds, si		! load rest of kernel segments
	mov	es, si		! kernel does not use fs, gs
	incb	(_k_reenter)	! increment kernel entry count
	mov	esi, esp	! assumes P_STACKBASE == 0
	mov	esp, k_stktop
	xor	ebp, ebp	! for stacktrace
				! end of inline save
				! now set up parameters for sys_call()
	push	edx		! event set or flags bit map 
	push	ebx		! pointer to user message
	push	eax		! source / destination
	push	ecx		! call number (ipc primitive to use)
	call	_sys_call	! sys_call(call_nr, src_dst, m_ptr, bit_map)
				! caller is now explicitly in proc_ptr
	mov	AXREG(esi), eax	! sys_call MUST PRESERVE si

! Fall into code to restart proc/task running.

!*===========================================================================*
!*				restart					     *
!*===========================================================================*
_restart:

! Restart the current process or the next process if it is set. 

	cmp	(_next_ptr), 0		! see if another process is scheduled
	jz	0f
	mov 	eax, (_next_ptr)
	mov	(_proc_ptr), eax	! schedule new process 
	mov	(_next_ptr), 0
0:	mov	esp, (_proc_ptr)	! will assume P_STACKBASE == 0
	lldt	P_LDT_SEL(esp)		! enable process' segment descriptors 
	lea	eax, P_STACKTOP(esp)	! arrange for next interrupt
	mov	(_tss+TSS3_S_SP0), eax	! to save state in process table
restart1:
	decb	(_k_reenter)
    o16	pop	gs
    o16	pop	fs
    o16	pop	es
    o16	pop	ds
	popad
	add	esp, 4		! skip return adr
	iretd			! continue process

!*===========================================================================*
!*				exception handlers			     *
!*===========================================================================*
_divide_error:
	push	DIVIDE_VECTOR
	jmp	exception

_single_step_exception:
	push	DEBUG_VECTOR
	jmp	exception

_nmi:
	push	NMI_VECTOR
	jmp	exception

_breakpoint_exception:
	push	BREAKPOINT_VECTOR
	jmp	exception

_overflow:
	push	OVERFLOW_VECTOR
	jmp	exception

_bounds_check:
	push	BOUNDS_VECTOR
	jmp	exception

_inval_opcode:
	push	INVAL_OP_VECTOR
	jmp	exception

_copr_not_available:
	push	COPROC_NOT_VECTOR
	jmp	exception

_double_fault:
	push	DOUBLE_FAULT_VECTOR
	jmp	errexception

_copr_seg_overrun:
	push	COPROC_SEG_VECTOR
	jmp	exception

_inval_tss:
	push	INVAL_TSS_VECTOR
	jmp	errexception

_segment_not_present:
	push	SEG_NOT_VECTOR
	jmp	errexception

_stack_exception:
	push	STACK_FAULT_VECTOR
	jmp	errexception

_general_protection:
	push	PROTECTION_VECTOR
	jmp	errexception

_page_fault:
	push	PAGE_FAULT_VECTOR
	jmp	errexception

_copr_error:
	push	COPROC_ERR_VECTOR
	jmp	exception

!*===========================================================================*
!*				exception				     *
!*===========================================================================*
! This is called for all exceptions which do not push an error code.

	.align	16
exception:
 sseg	mov	(trap_errno), 0		! clear trap_errno
 sseg	pop	(ex_number)
	jmp	exception1

!*===========================================================================*
!*				errexception				     *
!*===========================================================================*
! This is called for all exceptions which push an error code.

	.align	16
errexception:
 sseg	pop	(ex_number)
 sseg	pop	(trap_errno)
exception1:				! Common for all exceptions.
	push	eax			! eax is scratch register
	mov	eax, 0+4(esp)		! old eip
 sseg	mov	(old_eip), eax
	movzx	eax, 4+4(esp)		! old cs
 sseg	mov	(old_cs), eax
	mov	eax, 8+4(esp)		! old eflags
 sseg	mov	(old_eflags), eax
	pop	eax
	call	save
	push	(old_eflags)
	push	(old_cs)
	push	(old_eip)
	push	(trap_errno)
	push	(ex_number)
	call	_exception		! (ex_number, trap_errno, old_eip,
					!	old_cs, old_eflags)
	add	esp, 5*4
	ret

!*===========================================================================*
!*				level0_call				     *
!*===========================================================================*
_level0_call:
	call	save
	jmp	(_level0_func)

!*===========================================================================*
!*				data					     *
!*===========================================================================*

.sect .rom	! Before the string table please
	.data2	0x526F		! this must be the first data entry (magic #)

.sect .bss
k_stack:
	.space	K_STACK_BYTES	! kernel stack
k_stktop:			! top of kernel stack
	.comm	ex_number, 4
	.comm	trap_errno, 4
	.comm	old_eip, 4
	.comm	old_cs, 4
	.comm	old_eflags, 4